Automatic lathe and fluid circuit



April 1937- E. J. SVENSON 2,078,695

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Original Filed March 27, 1930 10 Sheets-Sheet 8 A 27, 1937. F. J.SVENSON AUTOIATIC LATHE AND FLUID CIRCUIT 10 Sheets-Sheet 10 Ell/6w"finestJSvmwon mwwu Hm w (U WM Patented Apr. 27, 1937 UNITED STATESPATENT OFFICE Application March 27, 1930, Serial No. 439,306

Renewed February 8, 1937 219 Claims.

My invention relates generally to automatically actuated materialworking apparatus, and particularly to apparatus such as automaticlathes equipped with a fluid or hydraulic system of control.

My present invention relates in a general way to apparatus or machinesof the type shown in my co-pending application, Serial No. 391,130,filed September 9, 1929. My present invention. however, contemplates theprovision of improved structural features, by means of which cuttingoperations and the like may be performed upon a work piece in a moreexpeditious manner. To bring to pass these desirable results, I proposeto provide a lathe or metal cutting machine. in which the constituentnumber of parts is reduced greatly, the structural arrangement isunusually rigid, and the combination of machine elements is exceedinglysimple. This simple yet durable 2o structural arrangement will enable mydevice to be operated with a minimum amount of skill and effort on thepart of an attendant, and it is also my purpose to so arrange thecooperating machine elements so as to render the control thereoffoolproof.

One of the important objects of my present invention is to provide, incombination with movable machine elements, such as tool carriages andthe like, a system of fluid control which is not only exceedingly simplein arrangement and economical to manufacture, but which is alsoexceedingly efllcient and positive in controlling the movement of thesemachine elements. To this end I propose to provide what I shallhereinafter refer to as a closed, valveless, fluid circuit. incombination with the machine elements, such as tool carriages and thelike. which are to be shifted. This novel and practical valveless fluidcircuit is not only adapted for use, in connection with the control ofmachine tools. but has a very broad application in various fieldswherein it is desirable to hydraulically effect the shifting of Anotherobject of my invention is to provide hydraulic means, in combinationwith a machine spindle, whereby a governed amount of movement of toolcarriages and the like may be obtained per revolution of said spindle.In other words, I propose to correlate the movement of the spindle withthe movement of the tool carriages, and in order to presenta practical,workable arrangement, I contemplate directly coupling with the spindle aplunger pump ofa new and practical design which is free from fluidleakage or slippos (CI. bit-4t) Still another object of my presentinvention is to provide, in combination with elements to be moved, suchas machine tool carriages and the like, a fluid system of control havinga closed high pressure circuit and an associated low pressure circuit,said high pressure circuit being employed for feeding purposes, and thelow pressure circuit for rapid traverse movements.

More specifically, my invention contemplates the provision of theabovementioned associated high and low pressure fluid circuits which areso arranged that each of said circuits is operable independently of theother.

A further object is to eliminate the necessity of employing complicatedfluid control valves and the like which have not only been veryexpensive, but which have also had a decided tendency by reason of fluidleakage. etc., to materially reduce the propelling effectiveness of thefluid pumping mechanism forming apart of the circuit which normallyincludes such control valves. To remedy this condition I propose toprovide a new and improved single control for governing the movement ofa plurality of machine tool carriages and the like. which may beconveniently manipulated without disturbing or affecting in any way thepropelling effectiveness of the pump included within the feedingcircuit.

A still further object of my invention is to provide. in combinationwith machines as above set forth. a continuously operable low pressurefluid propelling mechanism, such as a gear pump, and a high pressurefluid propelling mechanism, such as a plunger pump, which is directlycoupled with the machine spindle, the propelling effectiveness of one ofsaid pumps being totally independent of the propelling effectiveness ofthe other.

Another object is to overcome the disadvantaxes and difncultiesresulting from the use of clutch and other transmission arrangementswhich have been employed in connection with machine tools and the like.

These and numerous other objects and advantages will be more apparentfrom the following detailed description when considered in connectionwith the accompanying drawings, wherein- Figure 1 is a plan view of anautomatic lathe which is constructed and arranged in accordance with theteachings of my present invention:

Figure 2 is a front elevational view of the device shown in Figure l;

Figure 3 is a vertical sectional view taken longitudinally of themachine substantially along the line H of Figure 5;

Figure 4 is an end elevational view as viewed from the left of Figure 2,a portion of the upper structure thereof being broken away to moreclearly disclose the position of the upper fluid reservoir;

Figure 5 is a vertical transverse sectional view taken substantiallyalong the line 55 of Figure 2;

Figure 6 is an enlarged fragmentary sectional view taken transversely ofthe guide bar along the line 6-6 of Figure 2;

Figure 7 is a view of the device shown in Figure 6, said view beingtaken substantially along the line 11 of Figure 6;

Figure 8 is an enlarged plan sectional view of the main drive shaft andits associated driving elements;

Figure 9 is a detail sectional view of the clutch control mechanism,said view being taken substantially along the line 5-9 of Figure 8;

Figure 10 is a horizontal sectional view of the clutch control cylinderand piston, said view being taken substantially along the line ill-I0 ofFigure 9;

Figure 11 is an enlarged plan view of the dog supporting slide, themechanical mechanism controlled by the rear tool carriage for causingthe actuation of said slide, the main control or reversing valve, andthe valve for controlling the longitudinal movement of the frontcarriage, said valves being shown in section in order to disclose moreclearly the structural characteristics thereof;

Figure 12 is a vertical sectional view taken transversely of the reartool carriage substantially along the line l2l2 of Figure 1;

Figure 13 is a fragmentary vertical sectional view of the slide andassociated parts, said view being taken along the line l3l3 of Figure11;

Figure 14 is a plan view of the slide, said slide being shown in itsadvanced position as distinguished from the neutral position shown inFigure 11;

Figure 15 is a fragmentary transverse vertical sectional view takensubstantially along the line i5l5 of Figure 11;

Figure 16 is a. similar transverse sectional view taken along the line|6-l6 of Figure 11;

Figure 17 is also a transverse sectional view taken along the linel|--|| of Figure 11;

Figure 18 is a central longitudinal sectional view of the reversingvalve taken substantially along the line |8IB of Figure 11;

Figure 19 is a transverse sectional view of the right end of thereversing valve taken along the line i9l9 of Figure 11;

Figure 20 is a sectional view similar to Figure 19, disclosing therelative positions occupied by the valve ports when said valve has beenrotated so as to effect the discharge of fluid from one extremity of thevalve chamber for reversing pur- P Figure 21 is a central sectional viewof one of the high pressure plunger pumps disclosing the manner in whichfluid is received and discharged y a d D p;

Figure 22 is a transverse vertical sectional view of said pump takensubstantially along the line 2222 of Figure 21;

Figure 23 is a diagrammatic representation of the fluid circuit forcontrolling the movement of the tool carriages, the control or reversingvalve being shown in its neutral position;

Figure 24 discloses the reversing or control valve when said valve hasbeen shifted to its forward or starting position;

Figure 25 discloses said valve in its reverse position; and

Figure 26 is a fragmentary vertical sectional view of the continuouslyoperable gear pump.

Referring now to the drawings more in detail wherein like numerals havebeen employed to designate similar parts throughout the various figures,it will be observed that for the purpose of illustrating one practicalapplication of my invention I have shown the same as applied to anautomatic lathe. This lathe comprises a suitable base 30 which serves tosupport a machine frame 32, Figures 1 to 5 inclusive. In order to setforth more clearly the structural arrangement of my improved materialworking machine or lathe, I shall describe successively various generalunits which together constitute the machine in its entirety.

Head stock The head stock is designated-generally by the numeral 34,Figures 1 to 5 inclusive, and a casing portion 32:; of the head stockforms an integral upwardly extending section of the main frame 32, asclearly shown in Figures 2 and 3. Mounted within the head stock housing32a is a spindle 36, Figure 3, the reduced or outward extremity of thespindle being mounted within a suitable anti-friction bearing 38, andthe inner work supporting extremity of the spindle being mounted withina tapered bearing ill. The spindle is provided with a tapered opening 42and is also flanged to present a face plate 44. For a more detaileddescription of the specific arrangement of the spindle bearings,reference is made to my above mentioned co-pending application, SerialNo. 391,130. Rotation is imparted to the spindle 36 by means of a maindrive gear 46, which is keyed to the spindle and is driven through theagency of a pinion 18. Figure 8, and a pair of change gears 50 and 52.The gear 52 is connected directly to a man drive shaft 64, and themechanism for controlling the operation of this drive shaft will bedescribed later. Mounted upon the spindle 36 and rotatable with the gear46 is a roller chain sprocket 56 which is connected by means of asuitable chain 58 to gears of a pair of fluid propelling mechanisms orpumps 82, to be described later.

Tail stock The tail stock is indicated generally by the numeral 64,Figures 1 to 3 inclusive, and includes an upright frame section 66 whichis slidably mounted upon ways provided within the main frame 32. Theupper portion of the frame 66 presents a casing 88, and slidably mountedwithin the casing 66 is a sleeve Ill. Longitudinal movement of thesleeve 10 within the casing Gil is controlled by means of a hand wheelI! which is mounted upon a screw 14 extending within a screw block 16,Figure 3. The opposite extremity of the sleeve "I supports a centerpiece ll which is rotatably mounted within the sleeve by means ofsuitable anti-friction bearings an and 82. The specific structuralarrangement oi this center piece 18 and mountings therefor form a partof the invention disclosed in my above mentioned co-pending application.A suitable lever 84 is employed to secure the sleeve 10 in its variouspositions of longitudinal adjustment within the casing 68.

Front carriage The front carriage of the machine is designated generallyby the numeral 86, Fisures 2 and 5. This carriage structure includes atiltable base or frame 88 which is clamped upon a horizontally disposedcylindrical member or bar IIII by means of screws 92. The cylindricalbar 90 is mounted in suitable bearings 94 and 96, Figure 3, disposed onopposite sides of the front carriage frame 88. The bar 90 is capable oflongitudinal and rotatlve movement within said bearings. The frame 88extends upwardly and forwardly of the bar IIII, as clearly shown inFigure 5, the outer or forward portion of the frame being supported by adepending screw 98, the lower extremity of which carries a roller Hill.This roller rests upon a guide bar I02 which is pivotally mounted at oneend by means of a pin I04, Figure 2, the opposite extremity of said barresting upon the upper end of a piston rod IIIB which forms a part of afluid actuated mechanism I08. Slidably mounted in guides provided alongthe upper portion of the frame 88 is a slide III) which provides amounting for a tool holder III. This tool holder II! carries a suitablemetal cutting tool II4, Figure 5, which is secured in position by meansof clamping screws H6. The slide III] is adjustable toward and awayfromthe axis of a supported work piece II8 by means of a screw I20. Theupward movement of the guide bar I02 about its pivot I04 serves to swingthe front carriage 86 about the axis of the bar 80, and thereby carrythe tool II4 into proper cutting relation with respect to the workpiece. For a more detailed description of the structural arrangement ofthe front carriage frame 88 and its associated parts, reference is madeto my above mentioned co-pending application.

The upward movement of the piston rod I08 is occasioned in response tothe admission of a suitable fluid, such as oil, through a pipe line I22.Figures 2 and 23, which communicates with the chamber of a cylinder I24mounted on the front side of the machine frame 32. This fluid actsupwardly against a piston I26 at the lower end of the piston rod I06,and fluid from the opposite side of the piston I25 is discharged througha pipe line I28. The upward movement of the bar IE2 is interrupted by astop I 30, Figures 2, 6, and 7. The underside of this stop I" is formedwith an inclined surface, which is adapted to be engaged by acomplementary inclined surface at the free extremity of the bar I02. Theinclination of these surfaces is such as to cause the bar III! to beurged toward the front surface of the machine frame 32, and therebyprevent said bar from experiencing vibrations during the operation ofthe machine. The stop I" is vertically adjustable by means of a screwI32 which is supported by a bracket I34. Thus, the degreee of upwardmovement of the bar III! may be determined by adjusting the position ofthe stop I38 by means of the screw I42. The pipelines I22 and III areconnected to a constantly driven fluid propelling mechanism I36, Figures4 and 23, through the medium of a control valve Ill, said fluidpropelling mechanism and control valve to be described later in moredetail.

Pipelines I29 and III are also connected at opposite extremities of thecylinder I24, and these pipe lines establish communication between thecylinder I24 and a fluid actuated mechanism I 83, Figures 3 and 23,which is employed to impart longitudinal movement to the cylinder bar04.

This mechanism I includes a cylinder I in which a piston I3! isreciprocabie, and this piston I31 is connected to one extremity of thecylindrical bar 90 in any suitable manner, such as by means of a pistonrod I39. A pipe line I is connected to one extremity of the cylinderI35, and a pipe line I43 is connected to the opposite end of saidcylinder. The mechanism I33 is operated in timed relation with respectto the operation of the mechanism I IIB, as will later more fullyappear.

It is to be noted that the work piece and spindle rotate in thedirection indicated by the arrow in Figures 4 and 5.

Rear carriage The rear carriage of my apparatus is denoted generally bythe numeral I40, Figures 1 and 5. This carriage includes a slide I42mounted on guides I44, Figure 12, of a guide frame I48. This guide frameI48 is supported by the main machine frame 32, as clearly shown inFigures 5 and 12. Mounted upon the slide I42 is a tool holder I48 whichis adapted to carry a cutting tool I50, said tool being secured inposition by means of suitable clamping screws I52. Movement of the reartool holder and slide toward and away from the work piece I I8 isoccasioned in response to the movement experienced by a piston I54,which forms a part of the fluid actuated means which I have designatedgenerally by the numeral I56, Figures 5 and 23. This mechanism I56includes a cylinder I58, and the piston I54 which is reciprocabie withinsaid cylinder is connected to a piston rod I60. The outer extremity ofthis piston rod is adjustably connected to a bracket arm I62 dependingfrom and secured to the outer extremity of the slide I42. Pipe lines I64and I shown diagrammatically in Figure 23connect the oppositeextremities of the cylinder I58 with the high pressure pumping mechanism62, while pipe lines I68 and I'lfl connect the opposite extremities ofsaid cylinder with the main control valve I88, which is connected withthe low pressure pumping mechanism I36. Movement of the piston I54inwardly causes the tool IBII to be carried into operative associationwith the work piece for the purpose of making a facing cut across thework as distinguished from the peripheral cutting action of the tool H4.The fluid actuated mechanisms I08, I83, and I56 are operated in timedrelation in a manner to be described later.

Fluid supply for feeding purposes The mechanism which I have previouslydesignated by the numeral 62. includes a pair of plunger pumps I12 andIlla, Figures 1, 2, 4, and 21 to 23 inclusive. These plunger pumps areconveniently mounted upon the upper portion of the head stock frame 82aimmediately above the spindle 36. Each of these pumps I12 and Illaincludes a stationary cylinder block or housing I14, Figures 21 and 22,in which a plurality of radial pistons or plungers I" are reciprocablymounted. Movement is imparted to these pistonsby a ring I'll which issupported by an antifriction hearing I carried by a rotary drivingmember III. This rotary driving member I82 is coupled by means of atongue and groove connection I84 with a tapered or frusto-conical rotaryvalve I46 which is mounted within a complementary tapered bearing I88.The upper end of each of the chambers, in which the pistons I" arereciprocabie, is connected by means of 7 a passageway I with companionports I92 provided in the tapered bearing member I88, Figure 21. Thisrotary valve I86 is provided with peripheral ports I94 and ISla whichare adapted to register successively with the radially positionedpassageways I90. The peripheral port I91 communicates with an annularport I96 provided in the bearing member I", while the peripheral portI9la communicates by means of a longitudinal passageway I98 with achamber 200, which is enclosed by means of a casing 202. A suitableanti-friction thrust bearing 20. is provided to take up end thrustexperienced by the rotary valve, and an abutment screw 206 serves toadjustably position the valve within its bearing or seat. The chamber290 communicates with the pipe line I64, and the annular port or chamberI98 communicates with the pipe line I66.

When the driving ring I18 is positioned coaxially with respect to therotary valve I86, no movement will be imparted to the pistons I16, butwhen said ring I18 is eccentrically positioned with respect to the axisof the rotary valve, and the driving member IE2 is revolved, saidpistons will be reciprocated during each complete revolution of saiddriving member. Pivoted fingers 298 are interposed between theadjustable driving ring I18 and the pistons I16 so as to eliminate sidethrust during the movement of said pistons. R0- tation is imparted tothe driving member I82, or what might properly be called a couplingdriving member, through the agency of a journal or a sleeve 2"]. Thissleeve 2"! is supported by antifriction bearings 2I2 and 2 within anannular casing 2I6, said sleeve being keyed to a roller chain sprocketor gear 2I8. The driving or coupler member I82 is driven by the sleeve2M and is laterally shiftable within said sleeve through the agency of alongitudinal shiftable member 229. This member 220 is provided with anextension 222 which is angularly disposed with respect to the axis ofrotation of the journal or sleeve 2"), and by longitudinally shiftingthe member 229 as by means of the micrometer adjusting ring 224, thedriving member and its supported driving ring I18 may be sensitivelyadjusted.

While I have in a separate application, Serial No. 430,867, fliedFebruary 24, 1930, now matured into Patent No. 1,989,111, described andclaimed specifically the plunger pump or fluid propelling means shown inFigures 21 and 22, I have also described in some detail the structuralarrangement of this pump in the present application in order that thehigh pressure closed fluid circuit, about to be described, may beunderstood more readily. This will be appreciated more easily when it isunderstood that the plunger pump just described is of such a nature asto positively preclude fluid slippage or leakage. Heretofore, in usingconventional types of fluid plunger pumps, the leakage or slippage offluid through the rotary valve fittings, as well as other of the pumpfittings, has been so great as to positively prevent the use of suchdevices in a closed or valveless fluid circuit. The gear 2IB is directlyconnected with the gear 56 on the spindle 36 by means of the rollerchain 58 previously referred to. A single roller chain may be employedfor propelling both of the plunger pumps I12 and l12a, as clearly shownin Figures 4 and 23.

Rear carriage feeding circuit From the foregoing it will be apparentthat when rotation is imparted to the work supporting spindle 36, theplunger pump I12 will simultaneously be activated. This will result inthe displacement of fluid at high pressure by the pistons 16 through theports in the rotary valve and into the pipe line I68, and this fluid athigh pressure will be directed against the rear carriage piston I54.Fluid from the portion of the chamber in front of the piston I54 will bedischarged through the pipe line I84 to the intake side of the pump I12,or, in other words, into the chamber 200, Figure 21. This fluid will bedirected through the longitudinal passageway I98 in the rotary valve andthence into association with those pistons which are experiencing theirinward stroke. That is to say, fluid from the advancing end of the rearcarriage piston is employed to charge the pump I12, and fluid under highpressure from the discharge side of the pump is being employed toadvance the rear carriage piston. To relieve against the development ofexcessive pressures within the closed circuit, I provide a suitablepressure relief mechanism 226, as clearly shown in Figure 23.

The fact that I use a fluid propelling mechanism or pump which is freefrom the usual fluid slippage or by-passing, enables me to employ whatmay be termed literally a closed or valveless fluid circuit. Byemploying a closed fluid circuit, in combination with a non-leakablefluid pump which is directly co ected with a rotary portion of themachine, suc as the work supporting spindle, I am able to obtain agoverned amount of movement of a shiftable machine element, such as atool supporting carriage for each revolution of the spindle. In otherwords, the movement of the tool carriage is correlated with the rotarymovement of the work supporting spindle. This presents a'very practicaland extremely simple arrangement which has a very broad application inthe machine tool industry, as well as in other flelds.

Front carriage feeding circuit The pump l12a is identical inconstruction and operating characteristics to the pump I12 alreadydescribed, and is directly connected to the spindle 36 by means of theroller chain 58. A pipe line 228 is connected with the high pressure ordischarge side of the pump I12a, Figure 23, and connects with the pipeIII which, in turn, is connected to one end of the cylinder I35 of thefluid operated mechanism I33. The intake side of the pump HR: isconnected with the opposite extremity of the cylinder I35 through theagency of the pipe I43, a cut-oil valve 239, and a pipe line 232. Whenthe valve 230 occupies the position shown in Figure 23 communicationbetween the pipe lines I43 and 232 is broken, but when said valve isshifted in a manner later to be described, to a forward position, asindicated by the dot and dash lines in Figure 23, communication isestablished between the mechanism I 33 and the intake side of the pumpI12a. Thus it will be apparent that when the valve 230 occupies its openposition and rotation is ex perienced by the spindle 3B, the piston I31and consequently the front tool carriage 86 will be moved to the left,Figures 3 and 23. A conventional pressure relief mechanism 234 isconnected between the pipe lines 228 and 232 to relieve against thebuilding up of excessive pressures in the system. It will be seen thatthe feeding circuit, which includes the mechanism I33 and the pump I12a,is a closed circuit, and that the longitudinal movement of the frontcarriage is tax correlated with the rotative movement of the spindle.That is to say, for each revolution of the spindle, the front toolcarriage will be shifted to the left a predetermined distance, Figures 3and 23.

Low pressure fluid supply From the description given thus far it will beunderstood that forward movement of the rear tool carriage I48 will takeplace when the spindle 36 is rotated. I shall now proceed to describethe parts comprising a fluid circuit which includes the continuouslydriven low pressure mechanism or pump I36. This pump I36 is mounted atone end to the rear of the machine, as clearly shown in Figure 4. Thispump is driven by a roller chain 235 connected with a sprocket 236 whichis mounted upon the main drive shaft 54, Figure 8, and which isconnected to a continuously rotatable clutch member 238. This clutchmember is directly connected through ehe agency of the roller chain 248to any suitable driving means, such as an electric motor 242, Figure 4.

This pump I36 may be a gear pump, and I prefer to employ the type ofgear pump disclosed in my co-pending application, Serial No. 430,868,filed February 24, 1930, now matured into Patent No. 1,912,737. Theintake side of the gear pump I36 is connected with a fluid or oilreservoir 244, Figures 4 and 23, by means of a suitable pipe line 246.By having this reservoir 244 positioned above the pump I36, 011 iscontinuously supplied to the pump under slight pressure, and thus air isprevented from entering the fluid circuit. In order to prevent theintroduction of foreign matter within the oil of the reservoir 244, Iprovide a strainer or screen 248, as shown in Figure 4. The pump I36 ismounted upon a bracket 258 and may be shifted on said bracket in orderto make adjustments with respect to the roller chain 235. Variation indisplacement of the gear pump I36 may be obtained by merely adjustingthe position of a lever 252. This lever serves to operate a centralvalve 253, Figure 26, within the lower gear 255 of the gear pump. Thisgear 255 is pro vided with a plurality of radial passages 251 which areadapted to communicate with a valve port 259 to prevent oil frombecoming heated. The valve port 258 may also be adjusted so as to varythe fluid displacement, and this arrangement has a very practicalapplication in connection with automatic lathes and machines of likenature. For a more detailed description of this gear pump I36, referenceis made again to my above mentioned co-pending application.

Low pressure control for rear carriage The discharge side of the gearpump I36 is connected to a pipe 254 which, in turn, has a commonconnection with branch lines 256 and 258, as clearly shown in Figure 23.These branch lines are connected to the control or reversing valve I38.This valve I38, Figures to inclusive and Figures 23 to inclusiveincludes a central casing or housing 288, which is supported on theforward side of the machine frame 32. The housing 288 is capped at oneend by a casing section 268a, and at its opposite end by a casingsection 2682). A cylindrical valve member 282 is longitudinallyshiftable within the casing 268 and is provided with a series of valveports 264, 266, and 268. The valve member 262 may be manually shifted bymeans of a single control lever 218, Figures L 2, and 11, one extremityof said valve having a pivotal connection with the inner extremity ofthe control lever or handle 218. In Figures 11, 18, and 23 the valvemember 262 occupies what will be referred to hereinafter as its neutralposition. In this position the branch line 256, Figure 23, communicateswith the annular port 268, and this annular port, as shown in FigureI11, in that instant communicates with a chamber section 212 in thecasing section 268?). This chamber section 212 is connected by a returnpipe line 214, Fig. 23, an adjustable restricted oriflce 216, and a pipeline 218 with the reservoir 244. Thus fluid is circulated through thepump I38, the valve I38, and the restricted oriflce 216. Fluid from thebranch line 258 passes into the annular valve port 264 and from thisport is conducted through a longitudinal passageway 288 in the casing2680. to a chamber section 282 which is oppositely disposed from thechamber section 212. A passageway 284 connects the port 264 with thechamber 212, as clearly shown in Figure 11. In this manner the fluidpressure is balanced at each er'rtremity of the valve member.

By imparting a movement to the control handle or lever 218 to the right,Figure 11, the valve member 262 will be moved to the left so as tooccupy the position shown in Figure 24. This position will be referredto hereinafter as the forward position. Fluid is now directed from thebranch line 258 through the annular valve port 264 and thence throughthe pipe line I18 which connects with one extremity of the rear carriagecylinder I58. In this connection it is to be noted that the pipe lineI68 is connected also with the valve I38. Consider, for example, thatthe machine spindle 36 is at rest and the valve member 262 is shifted tothe forward position shown in Figure 24. Forward movement in response tothe pressure of the fluid directed into the cylinder I58 from the pipeline I18 will cause the rear carriage piston I54 to experience a rapidforward movement. This movement will be referred to hereinafter as therapid traverse movement which is required to bring the rear carriagetool I 58 into operative association with the work piece. Attention isdirected to a fluid actuated mechanism 286, Figures 1, 9, 10 and 23,which is operatively connected with a clutch mechanism 288, Figures 8and 9, later to be described. This fluid operated mechanism 286 includesa cylinder 288 and a piston 282 reclprocably mounted therein. Thispiston 292 is connected as by means of a piston rod 294 with means foroperating the above mentioned clutch mechanism 288. One extremity of thecylinder 288 is connected to the pipe line I18 by means of a line 288,and the opposite extremity of said cylinder is connected to the pipeline I68 by a pipe line 288. Upon shifting the valve member 262 to itsforward position as above set forth, the piston 282 of the mechanism 286is shifted to the left, Figures 10 and 23, so as to actuate the clutchmechanism 288 and thereby cause the main drive shaft 54 to be rotated.Rotation of this drive shaft obviously causes rotation of the worksupporting spindle 36. In response to the actuation of a mechanicallyshifted slide mechanism 388, Figures 11 and 14, later to be described,the valve 262 is returned to its neutral position shown in Figure 23, ata predetermined interval. This predetermined interval is determined bythe distance the tool I58 must be moved in order to bring said tool intooperative association with the work. In other words, the tool issubjected to a rapid traverse movement by the low pressure fluid so asto bring said tool quickly into operative relation with the work piece.With the valve 262 shifted to its neutral position, the low pressurefluid circuit including the pipe lines I68 and I16 is renderedfunctional ly inoperative, and the high pressure fluid circuit whichincludes the plunger pump I12 and the pipe lines I64 and I66 is renderedfunctionally operative. That is, fluid under high pressure is directedagainst the rear carriage piston I64 .to effect the feeding of the toolI56 across the face of the work piece. Thus it will be apparent that thelow and high pressure fluid circuits are operable independently of eachother.

When the feeding stroke of the rear carriage piston I64 has beencompleted, the valve 262 may be shifted manually or automatically to itsreverse position shown in Figure 25. When the valve is shifted to thisposition, fluid from the gear pump I36 is directed through the branchline 256 into the annular valve port 268 and thence through the pipeline I68 in the direction indicated by the dotted arrows, Figure 23.Reversing the direction of flow of the fluid in the pipe line I68 causesthe piston 292 within the clutch control mechanism 266 to be shifted tothe right, Figure 23, thereby disconnecting the driving motor from themain drive shaft 56, and consequently arresting the rotation of the worksupporting spindle 36. The rear carriage piston I64 is rapidly urged ina reverse direction, and fluid from the pipe line III! is returned tothe valve port 266, Figure 25. Fluid from this port 266 is directedthrough a longitudinal passageway 302 which communicates with the valvechamber 212. Thus the fluid is returned from the chamber section 212through the pipe line 2", the restricted orifice 216 to the reservoir 2.It should be understood that the adjustable restricted orifice 216supplants the usual spring operated relief valve, and has been foundmore practical and emciently operable than any fluid relief deviceswhich have been in common'use heretofore. The size of the orifice 216 isadjusted by means of a suitable valve member 211 which is mounted withina casing 219. The size of the orifice 216 may be adjusted to maintain apredetermined desired low pressure in the circuit for preventing any airfrom entering the circuit, and I have found that undue heating of thefluid which has been experienced heretofore in using spring valves andthe like is eliminated when my simple adjustable orifice arrangement isemployed.

When the rear carriage piston I54 reaches the limit of its rearwardstroke, the valve 262 may be manually or automatically shifted to itsneutral position, and the cycle of operation Just described may berepeated. It is to be noted that the spindle 36 is at rest during therearward movement of the tool I 66, thereby permitting an operator toremove the completed work piece and insert another work piece. The timeelement in operating machines of the type described is an importantfactor and, as stated above, my invention contemplates reducing to aminimum the time required to set up a work piece in the machine and tocomplete the cutting operations on said work piece.

Low pressure control for front carriage Thus far I have described themanner in which a low pressure fluid circuit is employed to impart rapidtraverse movement to the rear carriage cutting tool, and I shallendeavor now to describe the manner in which the low pressure fluid isemployed to control the front carriage tool Ill. As set forth above, thepipe line I28 is connected at one extremity to one end of the cylinderI24, Figures 2 and 23. The opposite extremity of this pipe line I 26 isconnected to the valve I36. Similarly the pipe line I22 serves tocommunicate the other end of the cylinder I24 with the valve I38, and itwill be seen that these pipe lines I22 and I26 are diametricallypositioned with respect to the pipe lines I66 and I'll alreadydescribed.

When the valve member 262 occupies the neutral position shown in Figure23, the circuit including the pipe lines I22 and I28 is functionallyinoperative, but when the valve 262 is moved to its forward position, asshown in Figure 24, low pressure fluid is directed through the pipe lineI22 and thus against the lower end of the piston I26. This causes therapid upward movement of the tiltable guide bar I62 and consequently arapid swinging oi the tool III toward the work piece. As stated above,the upward movement of the. Piston I26 is limited by the engagement ofthe free end of the guide bar with the adjustable stop I36. At apredetermined interval which is determined by the shifting of, a slidemechanism 366. later to be described, the valve 230, Figures 11 and 23,is shifted to the dot and dash position shown in Figure 23, and asdescribed above, the valve member 262 is shifted to its neutralposition. Under these conditions a high pressure fluid from the pipeline 228 passes through the pipe line Ill and thence into the cylinderI35 of the fluid actuated mechanism I33. This causes the front carriagecutting tool to be moved across the peripheral surface of the work pieceto the left, Figures 3 and 23, at a feeding rate. When the tool IIreaches the limit of its peripheral cutting stroke, the valve member 262is shifted manually or automatically to the reverse position, as abovedescribed. This causes the spindle 36 to stop rotating, and thus rendersthe fluid in the front carriage feeding circuit functionally inoperativeas a propelling medium. The flow of low pressure fluid in the pipe linesI26, I3I, I43, I, I29, and I22, Figure 23, is reversed, thereby causinga rapid reversal of the piston I31 which actuates the front toolcarriage. The front tool carriage is swung downwardly, therebymaintaining the tool I I4 out of engagement with the work piece duringthe reverse movement thereof. When the front carriage reaches itsstarting position, the valve 230, Figures 1]. and 23, is shifted to itsclosed position, and the valve member 262 is moved to its neutralposition.

It should be understood clearly that my invention is by no means limitedto the specific arrangement and timing of the tool carriages shown inthe accompanying drawings. In the foregoing description I have statedthat the front carriage is swung upwardly to bring the tool II4 intoproper position with respect to the work piece for making a peripheralcut longitudinally of said work piece. However, this front carriage toolmay be employed for actually making a cut during its movementtransversely of the work piece, as well as during its movementlongitudinally thereof. In other words, a feeding movement may beimparted to the front carriage about its support without departing fromthe broad scope of my invention. In fact, in certain instances it may bedesirable to employ only the swinging or oscillating movement of thefront carriage, and the longitudinal movement, if any, of the carriagemay be employed for additional purposes not specifically shown in thedrawings,

A device constructed in accordance with the teachings of my inventionmay be employed for making a great variety of cuts in a work piece, andhence it should be understood clearly that the specific arrangement andtiming of the cutting tools as described above is representative of onlyone of a wide range of constructions which might be employed.

Automatic fluidcontrol mechanism Means for automatically controlling themove ment of the valve member 262 and the valve 230 includes the abovementioned slide mechanism 300.1 lgures 11 to 14 inclusive. This slidemechanism comprises a horizontal slide 304 which carries a plurality ofdogs 303, 303, 3), M2, and 3i3. The movement of the slide 304 iscontrolled by the rear carriage slide I42. The bottom of this slide I42supports a rack bar 3l4 which drives a ear 3l6, and this gear 3|6actuates a shaft 3I8 which carries a bevel gear 320. This bevel gear 320meshes with a companion bevel gear 322 carried by a shaft 324. The outerend of this shaft 324 carries a pinion or gear 328. This gear or pinion326 is secured irictionally upon the shaft 324 by means of a suitablecollar 328, Figure 15, and associated clamping nut 330. The frictionalmounting of the gear 326 upon the shaft 324 is such that said gear willrotate with the shaft for driving a rack bar 332 which is carried on theunderside of the slide 304. If the slide 304 meets with resistancebeyond a predetermined amount, the gear 326 will not rotate with theshaft 324, thereby preventing any parts of the slide from beingsubjected to undue strains and stresses. In Figure 11 I have shown theposition occupied by the slide 334 when the machine is at rest and thecontrol valve member 262 occupies the neutral position shown in Figure23. Consider now that the valve member 282 is moved to its forwardposition shown in Figure 2.4 by shifting the control handle 210 to theright, Figure 11. This control handle carries an arm 334 which makes aslotted connection with a slidable shaft 336. This shaft 336 is mountedwithin a sleeve or casing 338, which is formed integral with the casingsection 260b, and the outer end of this shaft 336 detachably supports adepending lug 340. As the rear tool carriage I42 experiences its forwardmovement, the slide 304 is moved to the right, Figure 11, and the dog3"! is eventually carried into engagement with the depending lug 340,thereby causing the shaft 336 to be shifted rearwardly. This causes thevalve member 262 to be moved to its neutral position. At a predeterminedinterval, which is in accordance with the nature of the work piece, thedog 306 is carried into engagement with 9. depending lug 342 detachablysupported at the outer extremity of the valve member 330. This causessaid valve to be moved to its open position so as to effect theiongitudinal feeding movement of the front tool carriage. As the slide304 continues to move to the right, the dog 3l2 eventually engages abell crank 344, and this engagement takes place when the tool carriageshave reached the limit of their advancing strokes. The bell crank 344 isconnected to one end of a rack bar 346 which traverses the upper portionof the valve mechanism I38, as clearly shown in Figures 18 to 20inclusive. This rack bar 348 meshes with teeth formed on the peripheralsurface of a rotary balancing membcr 348, and the shifting of the bellcrank as above described causes the member 348 to be shifted from theposition shown in Figures 13 and 19 to the position shown in Figure 20.When this balancing member is shifted to the position shown in Figure20, pressure of the fluid within the chamber section 282 of the valveI33 is relieved, said fluid passing from the chamber section through aport 350 and thence into a return pipe 352 which connects with the oilreservoir 244. Relieving the pressure in this chamber 282 causes thevalve member 262 to be unbalanced, and thus automatically shifted to thereverse position shown in Figure 25. A spring 354 at one extremity ofthe rack bar 346 causes said bar to be automatically shifted outwardlywhen the dog 3i2 is moved away from the bell crank 344, therebyautomatically reestablislzing the closed position of the valve 343.

At this point it should be understood that automatic means, other thanthe unbalancing arrangement just described, may be employed forimparting a reversing movement to the valve member 262 without departingfrom the spirit and scope of my present invention. The mechanism wherebythe fluid pressure on said valve member is unbalanced is particularlyapplicable in instances where a very quick reversal of the valve memberis required. However, in other instances it may be advisable to employ asimple mechanical control, which will directly engage the valve member232 to effect the reversal thereof. Such an arrangement is not shown inthe drawings, but my present invention contemplates means other than thespecific valve unbalancing arrangement for effecting the automaticshifting of the valve member 262 within its casing or housing 260.

When it is desirable to manually control the shifting of the valve 262,it is only necessary to shift the lugs 340 and 342 out of the pathfollowed by the dogs on the slide 304. This is readily accomplished bymerely pulling outwardly on the pins which support these lugs and thenimparting a slight rotary movement thereto, so as to shift said lugs outof the path of movement of the dogs on the slide. Obviously this may beaccomplished without disturbing the position of the dogs on the slide.Thus, in instances where the operator wishes to have complete manualcontrol of the machine, it is only necessary to quickly shift thenormally depending lugs 340 and 342 in the manner described.

Shifting the valve member 262 to its reverse position causes the reartool carriage to be moved rearwardly and the front tool carriage to bemoved toward its starting position. When these tool carriages reach thelimit of their movement, a dog 3i 3 on the slide 304 engages thedepending lug 340, and thereby automatically moves the valve member 262to its neutral position, and the dog 303 closes the valve 330, Figure11.

Clutch and driving mechanism The clutch mechanism 288, Figure 8, issimilar to that disclosed and described in connection with my abovementioned co-pending application and may be of any practical design. Themechanism disclosed includes a clutch memher 356 which is axiallymovable in response to the movement ofactuating arms 353. The movementof the member 356 into engagement with a rotary friction disk 360, inresponse to outward movement imparted to the arms 358. causes power tobe applied to the drive shaft 54 from the prime mover or motor 242. Thisoutward movement of these arms 353 is occasioned in response to theshifting to the left of the piston rod 294.

This movement of the piston rod 264 causes a horizontally disposed arm362 connected there- I with to rotate a vertical shaft 364 which, inturn, causes arms 366 supporting a yoke 368 to move a member 316, Figure8, into engagement with the arms 356. When the piston rod 294 is movedto the right, Figure 10, the clutch elements are disengaged and theprime mover 242 is disconnected from the drive shaft 64. The outer endof the drive shaft 54, Figure 8, carries a. pulley 312 which may beconnected to a cooling pump (not shown). The specific structuralcharacteristics of the clutch mechanism is a part of my presentinvention, only as it enters into the general combination, and thereforeit should be understood that said invention is not limited in any senseto a particular type of clutch mechanism.

This clutch mechanism 288 and associated driving elements including themain drive shaft 54, the change gears 56 and 52, as well as the pinion48, is supported by a bracket 314 and a bracket 316. These brackets aredetachably mounted upon the rear side of the head stock casing 321:, asclearly shown in Figure 8. By supporting these parts which comprise thetransmissionin the brackets 314 and 316, I am able to subass semble theparts before securing the entire unit to the head stock. Thisarrangement consider- Till ably reduces the amount of machining work onthe head stock and bed, and also enables said head stock to be securedconveniently and rigidly in position upon the machine base. This is ofutmost importance in connection with the design of machines which are tobe subjected to heavy duty operating conditions.

Statement of operation Consider that the dogs on the slide mechanism 366have been properly positioned on the slide 364, that is, in accordancewith the desired timing of the movements of the rear and front cuttingtools. Consider also that the electric motor or prime mover 242 isoperating and thus driving the gear pump I36. A work piece is secured inposition between the head stock spindle and the tail stock center piece.After the work has been set up properly, the operator moves the controlhandle 216 to the right, thereby shifting the control valve 262 to itsforward position as shown in Figure 24. This causes low pressure fluidfrom the gear pump to effect a rapid traverse movement of the rearcarriage tcol toward the work piece and also causes the front carriageto be swung about its axis so as to bring the tool supported therebyinto proper position for making a peripheral cut upon the,

work piece. The clutch control mechanism 286 is also activated by thelow pressurefluid so as to operatively connect the main' drive shaft 54and consequently the spindle 36 with the prime mover. This causes theactuation of the high pressure variable displacement plunger pumps I12and NM. The dog supporting slide 364 is moved in response to the forwardmovement of the rear carriage slide, and at a predetermined interval thecontrol valve member 262 is shifted to its neutral position through theaction of the dog 3I6, and the valve 236 is shifted to its open positionthrough the action of the dog 366. The plunger pumps I12 and H20 are nowincluded within a closed valveless fluid circuit, the displacement offluid from the pump I12 causing a forward feeding movement of the rearcarriage tool across the face of'the work piece,

and the fluid displaced by the pump I124: causing the front carriagetool to be fed longitudinally of the work piece. Upon the completion ofthe feeding stroke of these cutting tools, the valve member 262 isautomatically shifted to its reverse position in response to theengagement of the dog 3I2 with the bell crank 344. The engagement of thedog with the bell crank 344 causes the valve member 346 to be rotatedsufllciently to eflect the release of the fluid from within the chambersection 262, thereby unbalancing the fluid pressures at the oppositeextremities of the valve member 262. The shifting of the valve member262 to the reverse position causes a reversal in the direction of flowof fluid in the low pressure circuits, with the result that the clutchcontrol mechanism 266 is operated to disconnect the spindle 36 from theprime mover. The reversal of flow in these circuits also causes a rapidreverse movement of the front and rear tools, and when these tools reachtheir starting position the dog 3|! engages the depending lug 346,thereby shifting the valve member 262 to its neutral position. The workpiece does not rotate as the cutting tools are reversed, and hence theoperator may use this period to good advantage in removing the workpiece and inserting another. After a subsequent work piece has been setup in the machine a repetition of the cycle just described is obtainedby merely shifting the control handle 216 to the right.

As a precaution against the possibility of leakage in the cylinders ofthe fluid actuated mechanism I66, I33, and I66, which might result fromwear or improper adjustment, I employ bleed passages 386 and 362, Figure18, in the valve casing 266. Experimental work has shown that theserestricted openings 366 and 382 will serve to replenish any fluid whichis lost as a result of the above mentioned improper adjustment. Thisexperimental work disclosed that it is not necessary to employ theserestricted openings when the fluid actuated mechanisms are in properadjustment, but I have found that a 3'! inch hole will not injure orcause any difference in action in the closed valveles; circuit duringthe feeding stroke if the load of the piston is of a puisative nature.The area of one of the cylinders in the average construction isapproximately ten square inches, and therefore it will be understoodthat it is impossible to place any load on the piston which would forcethe fluid through a 1 inch hole so as to cause a pulsated action. Asstated above. these holes 386 and 362 are merely employed in instanceswhere compensation must be made for the adjustment of the cylinders.These holes merely serve as compensating means to prevent the buildingup of too great a pressure on the advancing side of the piston.

Summary by A system oi control enables the use of a single, simple,three-position valve which is connected only to a low pressure circuit.In other words, leakage or fluid slippage which has been experiencedheretofore in using conventional control valves in high pressure fluidcircuits, is completely obviated by my improved arrangement. In mydevice, the high pressure circuit is operable independently of the lowpressure circuit, and no valves of any kind are required in said highpressure circuit. Through the agency of this closed valveless circuitcombined with my improved variable displacement plunger pump directlydriven from the work supporting spindle, I able to obtain apredetermined feeding movement of an actuator piston per revolution ofthe work supporting spindle. The tapered valve arrangement combined withthe stationary block for supporting the radial pistons, presents apumping structure which is particularly adaptable for use in closedcircuits. This results from the fact that the tapered valve positivelyprevents leakage toward its smaller end, and any slow leakage of fluidat its larger end is redirected to the intake side of the pump. This isto be distinguished clearly from pumping devices which have beenemployed heretofore, wherein a high degree of fluid slippage has beenexperienced along the surfaces of the rotary valves, thereby causing theoverheating of the fluid and a material decrease in the propellingefficiency of the pump. In other words, my invention provides, incombination with an actuator piston, a pumping mechanism havingvalveless ducts extending between said pump and the actuator piston, andthe fluid medium confined within said parts being substantiallynon-compressible, imparts a positive and constant propelling forceagainst the actuator piston. Thus, the high pressure circuit may betermed aprimary circuit, and the low pressure circuit may be termed asecondary circuit, said primary circuit being used for feeding purposes,and the secondary circuit for the purpose of rapid traverse. It shouldbe understood that means other than that disclosed in the drawings, maybe employed for imparting rapid traverse move ments to the tools withoutdeparting from the spirit and scope of my present invention. In

other words, my present invention contemplates other mechanicalarrangements which would serve to impart such movements at predeterminedintervals to the tool carriages.

It will be apparent from the foregoing description that my inventioncontemplates the provision of a hydraulic actuator system forcontrolling the movement of machine parts and the like in such a mannerthat uniform movement of the machine part is positively effected indirect accordance with volumetric displacement of fluid to the intakeportion of the actuator cylinder irrespective of variations in fluidpressure or load to which the actuator piston may be subjected duringits feeding stroke.

To explain this advantage from a more practical viewpoint, I callattention to the fact that the present invention is particularlyadaptable for use with metal cutting machines, such as lathes, millingmachines, and the like, wherein the tool or work is frequently subjectedto varied degrees of resistance during the cutting operation. Forexample, in a milling machine equipped with the present hydraulic systemof control, the table of the milling machine carries the work and ismoved horizontally by the hydraulic actuator past a rotary cutter. Ifthe cutter is rotating in such a direction that the teeth of the cutterexert a force which is in a direction opposite to the direction ofmovement of the table, then the pressure of the fluid on the trailingside of the piston is greater than the pressure of the fluid on theopposite side. On the other hand, if the cutter is rotating in adirection so that the cutting teeth exert a force in the same directionas the table, then the pressure of the fluid on the advancing side ofthe actuator piston will be greater. It will be apparent that, unlessthe hydraulic circuit is arranged in a particular manner to meet theseconditions, the table will experience a non-uniform or pulsating action,due to the variations in fluid pressure on the opposite sides of thepiston.

In the present invention the plunger pump is connected to the oppositesides of the actuator cylinder in such a manner that a uniform movementof the tool or carriage propelled by the actuator piston is positivelyeffected in direct accordance with the volumetric displacement of fluidto the intake portion of the cylinder irrespective of the resistanceencountered by the tool or carriage in its travel. That is to ay, eventhough a milling machine carriage or lathe tool meets with varyingdegrees of resistance during its travel (resulting from soft spots inthe metal, or non-circular form of the part to be turned in the lathe),the volumetric displacement to the intake side of the cylinder continuesat a uniform rate, and therefore the piston must likewise traveluniformly in accordance with such displacement.

The plunger pump ls connected with the advancing side of the piston insuch a manner that fluid confined in front of the advancing side of thepiston must be returned at the same rate as the fluid displaced to theintake side of the actuator piston by the plunger pump. By thisarrangement the fluid bodies controlled by the action of the plungerpump operate similarly to a lead screw in a lathe wherein no slippagetakes place.

Another example in which a variation in fluid pressure occurs onopposite sides of the actuator piston is in a machine, such as a drillpress having a vertically disposed drill holder, which must bevertically reciprocated. By employing a vertically reciprocable actuatorpiston within a cylinder in conventional machines, some auxili ary meansmust be provided to prevent gravity from acting upon the piston so as tourge it downwardly. In the present invention no auxiliary means need beprovided to prevent gravity or other forces from shifting the actuatorpiston, because when the fluid body is positioned beneath a verticallydisposed piston, it is locked in position, and, although it is subjectedto greater pressure than the fluid on the opposite side of the piston;no variation nor non-uniformity of piston movement will occur. That isto say, the uniform movement of the piston which drives the machine partis positively effected in direct accordance with the volumetricdisplacement of the fluid (not pressure) to the intake portion of thecylinder.

The phenomenon just described should also be considered in connectionwith the variations in fluid pressure on the opposite sides of theactuator piston which result when the tool carriage is suddenly changedfrom rapid traverse to feed. It will be recalled that during the rapidtraverse of the machine part or carriage, fluid from the largedisplacement gear pump passes through the main control valve into oneend of the actuator cylinder, and fluid from the opposite end of saidcylinder passes through said valve and is returned to the reservoirthrough a restricted oriflce which sets up the required degree of backpressure. The instant that the main control valve is shifted from itsrapid traverse to its neutral or feeding position, the opposite sides ofthe feeding circuit are completely sealed from the rapid traverse fluid,and the momentum of the tool carriage will cause a sudden building up ofpressure at the advancing side of the actuator piston and a suddenlowering of fluid pressure on the opposite side. This sudden building upof pressure might properly be referred to as a preloading action". Thatis to say, the fluid sealed within the, forward side of the actuatorcylinder experiences a sudden increase in pressure at the instant thatthe small displacement or feed pump becomes functionally operative. Thispreloading action serves to positively prevent any stuttering orpulsating efl'ects when the tool begins its cutting operation.Heretoi'ore considerable difllculty has been experienced withconventional hydraulic systems of control when the fluid pressure on theopposite sides of the actuator piston varies. In fact, it has beencommon practice to employ relief valves to pernut the fluid to by-passwhen sudden increases in fluid pressure are experienced, and obviouslyunder such conditions no preloading of the fluid can take place, andhence a non-uniform or stuttering action takes place when the shiftablemachine part changes from one speed to another. Therefore, it will beapparent that this sudden increase in pressure or preloading actionconditions the fluid on the intake side of the small displacement orfeed pump in readiness to charge said pump the instant that the maincontrol valve clips off the low pressure fluid and renders the closedfeeding circuit functionally operable. At this point it should also beunderstood that various types of prime movers, such as multi-speedmotors. may be employed to impart rotation to the machine spindle.

Attention is called to the fact that by employing the secondary lowpressure circuit, in combination with the primary or high pressurecircuit, I am able to constantly change the fluid in said high pressurecircuit. This will .be clear when it is understood that each time thesecondary circuit functions, fluid from said circuit is taken into oneend of the actuator piston cylinder and discharged from the oppositeend. This prevents the fluid in the closed primary circuit fromdeteriorating.

By having the transmission elements carried by brackets which aredetachably mounted upon the head stock frame, a very practicaltransmission unit is presented. This may be readily assembled beforemounting upon the machine, and while in operation said unit does notimpart any undue strain on the head stock frame. The changeable gearsprovide a convenient arrangement for varying the spindle speed, and itwill be under stood that other forms of speed varying devices may beemployed which come within the scope of my present invention. The gearpump is convenientl-y connected to the transmission and is readilyaccessible for purposes of replacement and the like. By employing avariable displacement gear pump, as shown, the fluid displacement in thelow pressure circuit may be varied without varying the speed of theprime mover. By having the oil reservoir placed at a higher level thanthe gear pump, oil is constantly supplied under slight pressure to saidpump, and air is completely eliminated from the circuit. It is to benoted that the prime mover or motor is housed in a ventilated chamberand may be adjusted for taking up wear in the roller chain. Theautomatic control of the clutch by means of the mechanism includedwithin the low pressure circuit, provides a very simple and positivelyacting device. It is to be noted also that this control is operatedindependently of the high pressure fluid circuit. It should beunderstood that the invention is not limited to the specific arrangementof the disclosed clutch construction, but contemplates the provision ofa clutch control which will timingly control the rotary movement of thework supporting spindle.

It will be understood from the foregoing description that the dischargeside of the rapid traverse or gear pump I is never connected with theintake side of the feed pump during the operative functioning of thefeed pump. That is to say, when the actuator I56 moves forwardly inresponse to the action of the pump I", fluid discharged from saidactuator is subjected to back pressure setup within the restrictedoriflce 21!, and this back pressure exerts itself upon the fluid withinthe conduit I which connects with the intake side of the plunger pumpIII. In this manner air is positively precluded from entering the intakeside of the feed circuit during the rapid forward advancement of theactuator piston Ill. when the actuator piston IN is moved in a reversedirection, the plunger pump I72 stops, and hence, while the duct orconduit I communicates with the fluid discharged by the gear pump I", nomovement of fluid in the duct I or I takes place, and thus air ispositively precluded from entering the feed circuit. During the reversemovement of the actuator piston I the fluid discharged thereby issubjected to back pressure set up by the restricted orifice 2", and thispressure exerts itself upon the fluid in the duct I, thereby preventingany movement of the fluid in said duct. In the above-described manner,any air which may be taken in through the action of the gear pump I" ispositively prevented from entering the feed circuit. This is of theutmost importance in preventing the actuator, and consequently the tooldriven thereby, from experiencing a pulsating movement. By having thisconstruction. the

feed pumps may beplaced above the level of the reservoir without thepossibility of any fluid flowing out of the feed circuit, and withoutthe possibility of air being introduced within said circuit.

From the foregoing it will be apparent that I- provide two independentcircuits. namely, a high pressure circuit which is connected to theplunger pump, and a low pressure circuit which is connected to the gearpump. The low pressure circuit is initially placed in operative positionby shifting the main valve, and at this interval the high pressurecircuit is in an inoperative state. The actuation of the low pressurecircuit causes the high pressure circuit to be rendered functionallyoperative. and the low pressure circuit is then rendered functionallyinoperative. thereby allowing the high pressure circuit to impartfeeding movement to a tool carriage independently of any other circuit.At a predetermined interval, and in response to the move-

